


mutualism

by orphan_account



Category: Sherlock (TV), Sherlock Holmes & Related Fandoms
Genre: Age of Sail, Alien Biology, Ambiguous Orgasms, Anglerfish Metaphors, Breathplay, Cecaelias, Cilophytes, Compromise, Consent Play, Drowning, Fake Science, Kissing in the Rain, Lighthouses, M/M, Merlock, Mild Sexual Content, Mythical Beings & Creatures, Ocean, Octopi & Squid, Risk Aware Consensual Kink, Roleplay, Science Fiction & Fantasy, Tentacles, Trust
Language: English
Status: Completed
Published: 2013-05-20
Updated: 2013-05-20
Packaged: 2017-12-11 20:09:27
Rating: Mature
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 2,627
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/802720
Author URL: https://archiveofourown.org/users/orphan_account/pseuds/orphan_account
Summary: <blockquote class="userstuff">
              <p>"<b>Mutualism</b> is a sometimes symbiotic association between organisms of two different species in which each is benefited. Mutualistic arrangements are most likely to develop between organisms with widely differing living requirements." - <em>Encyclopaedia Britannica</em></p>
            </blockquote>





	mutualism

**Author's Note:**

  * For [cypress_tree](https://archiveofourown.org/users/cypress_tree/gifts).



> Note the "consent play" tag (the word _no_ is used and ignored by mutual agreement). Never roleplay with a mythical maritime death god you don't completely trust. The lines about brasswork are from [a poem](http://www.jacksjoint.com/brasswork.htm) by lightkeeper Fred Morong, and this particular alternate universe is an outtake from [a longer story](http://www.tumblr.com/tagged/a+pool+so+pitchblack) I'm writing collaboratively with [tree](http://cypress-tree.tumblr.com/). Unbeta'd.

The lightkeeper traced his lips with the tip of his tongue and tasted salt. 

The downpour had slowed to a drizzle, but every puff of breeze had John Watson shivering, skin goosepimpled beneath his wet shirt. Occupied as he was, though, the cold was more than bearable. 

Pale arms clung heavy around John’s neck, pulling him down toward the water. His small craft was tipping, perilously close to capsizing-- but wet fingers curled at his nape, a wet mouth distracted him from danger. They were both so slick with saltwater and rain that it was impossible to tell where a kiss or caress began and ended, each touch sliding slippery into the next. 

Time passed very pleasantly until the glimmer of grey noon sun caught John’s eye, a reflection warped on the waves. He pulled away from his companion with a sigh. 

“It’s clearing up,” he observed. Daylight was nudging the clouds apart and the drizzle had abated. Soon it would stop, altogether. John turned toward the rocky coast, where warmth and duty waited. They had drifted a few hundred meters from his anchorage. 

When he looked to the water again, Sherlock had ducked out of sight. 

“Don’t be like that.”

There was a bubbling sound, and John grinned. “You know I can’t hear you.” 

Two bluewhite hands slid smoothly up the side of the boat and gripped the gunwale. John caught hold of them and squeezed. 

A low voice muttered, “Fine. Tomorrow.”

John leaned over the side until he could see Sherlock’s pale, unhappy face, submerged to the jawline. He dipped his fingers in the drifting curls, half expecting them to come away inkstained.

“Find some old bones and tell me their story,” John said, quietly. 

The siren frowned. “There are no more bones to find.”

“Not in the whole ocean?”

“I’m not going to search the whole ocean to find you a story,” the creature retorted, rising to nuzzle his cheek into the calloused palm. Something like sadness shadowed John’s smile, at that, and the siren closed his eyes against it.

“It’s your own fault,” he mumbled, adding quickly, “about the bones.” 

John laughed. “I’m doing my job. I can’t be blamed if that puts you out of work.” He gripped a lock of hair and pulled.

“Is that so?” Sherlock grinned, uncovering a startling array of sharp teeth. “ _What robs him of health, of vigor and vim?_ ”

“ _What makes him look ghastly, consumptive and thin?_ ” John sing-songed. 

“ _What causes despair--_ ” A dripping hand rose and hooked a finger in the sailor’s collar. “ _And drives him to sin?_ ” Sherlock hissed on the last sibilant, body rising out of the water until their faces were a breath apart. 

“ _It’s brasswork,_ ” John retorted, lunging playfully out of reach, boat rocking with the sudden shift in weight.

Sherlock vanished, diving under the boat and emerging on the other side to catch John’s wrist just as he stuck out his arm for balance. His grip was tight enough to make John’s fingertips prickle and go cold, if they could get any colder-- but his grin was enchanting, sharp and white as crusts of brine salt bleached by the sun. 

“What do you want with me, sea-devil?” John demanded, voice dropping to mimic the growl of fishermen in fireside tales. 

Sherlock’s eyes gleamed at the invitation to play, his glee almost childlike in its simplicity. With a forceful twist he stretched out John’s arm and pushed up his soaked sleeve, baring sinewy skin.

“Interesting,” he hummed, voice plummeting to a bass that raised the hairs on the back of John’s neck. “These are a sailor’s bones.” A pale fingertip ran up along the hidden radius and down the ulna to pause at the wrist. “But not just a sailor. Thirty-- thirty- _five_ years old,” pale eyes moved over John’s limb like a scalpel, peeling back flesh and muscle. “A small frame, but strongly built; a soldier, not a sail-hauler. The labour has left its mark-- little fractures, like hairs,” his fingers traced ellipses. “But that was earlier in his career. Bursts of sustained exertion exchanged for a steady, slow grind.”

John was smiling. “What, like a farmwork?”

“Not the way this man was dressed. Not the way he died. And the wrists,” he rolled a cold thumb over the small bones as he spoke, “say hefting and polishing. Lots of polishing. He kept a lighthouse.”

“How did he die?” John dared. 

“He wasn’t shot.”

“No?” 

“There is a wound,” the siren’s voice was solemn, “but long healed. His death was not caused by violence or injury.”

John swallowed, audible even over the waves. “What, then?”

Sherlock eased the lightkeeper’s arm down until saltwater licked his knuckles. He pressed his lips to the pulse in the bend of John’s elbow and whispered, “He was drowned.” 

Far overhead, a fulmar stutter-called to its cliffbound mate. An unspoken proposition hung in the air, an invitation to adventure. The spellbreaking drop of rain could fall at any moment, and put an end to deliberating. 

“Tell me how,” John whispered, and the decision was made. 

“I could show you.”

John shook his head.

“Come with me.” Sherlock’s voice rose like steam from the water, growing more reverberant and strange with each word. “I’ll show you.” 

John shivered. “I think I’m beginning to understand what happened.”

“No--” The siren rose from the water, naked torso glistening. John edged toward the far end of the boat, then stilled: there was nowhere to flee. “I don’t think you do. I don’t think you can even imagine the things my sailor saw, before the end.” 

The creature rested his weight on the gunwale, and John could see the beginnings of shiny, purple-black skin fading up toward his hipbones. He recalled the sight of Sherlock sprawled full-length on the sand, and tried to picture how much of him was still submerged, twisting and stroking against the wooden planks beneath him. 

“Is that how you lured him in?” John asked. His gaze followed a rivulet that trickled from Sherlock’s jaw down to his collarbone and over his fishbelly pale chest. “Promising to show him the secrets in the deep?”

Sherlock’s grin crinkled in a way John knew no tale-telling sailor would ever believe. “Things no man has seen.” 

John scoffed, crossing his arms over his chest, “Sand and fish and bones, and more sand.”

“Coral the colors of wine spilt at sunset. Pearls that grow in patterns like fine lace,” Sherlock was making full use of his inhuman baritone, and John could feel the wood of his small craft hum like a breathing thing. “Blue and green lights that shine in the deep, and dance up to cover the surface like oil at midnight. Chimneys that glow red hot under a hundred fathoms of cold water, worms that wind through whalebone like a pretty girl’s ribbons...”

John leaned weakly on his elbows and sucked in a breath through parted lips. 

“You will come,” Sherlock said, all delighted teeth. His body arched over John’s like a rebel figurehead. 

Game or no, John was breathless. “I-- _no_.” What a wonderful struggle it was, to force that word from his tongue. “No, I can’t.” He turned his face away and gave himself a shake.

Sherlock stared, rapt in admiration. 

“I can’t go.” John spoke through gritted teeth. “I would drown.”

“But--” Sherlock reached to stroke a tanned cheek with two fingers. “You’d be with me.”

John closed his eyes, pressing nearly flat against the side of his boat in the attempt to distance himself from the siren’s voice. He mouthed “no”.

The boat’s gentle rocking was arrested with a thump. 

“ _Yes._ ” Sherlock’s reply was a hiss. As if giving body to the sound, a tendril like a dribble of ink curled over the side, close to where John's head rested. 

Shiny and wormslick, tapering to a point, the flesh-thing felt its way to John’s ear. It touched him and he shuddered, eyelids snapping open. John sat bolt upright in the center of the boat, staring at the appendage as if he had never seen it before, startled and a little fascinated. 

Sherlock hardly bothered to hide his delight.

Two, then five, six, eight limbs leaked over the sides. They nosed the oaken planks, the bilgewater, tasting their way towards John’s legs. Sherlock loomed, unmoving; a disconnected puppeteer, eyes fixed on John. 

John held out his hand and gaped when one of the boneless limbs tongued around his wrist. When he tried to pull free, the loop tightened. They were finding his ankles, now, and his legs went rigid at their touch. He rolled his arm in its bindings to reveal purplish suckered rows lining the underside, trembling like round, empty mouths. 

“If you won’t come willingly,” Sherlock murmured, “then you will be my prey.”

John fought, wordlessly. The boat bucked and nearly capsized, flooding with heaving limbs. Spots of pigment flushed red over darker skin, shifting Sherlock’s color as he invaded the flimsy craft. John felt serpentine coils push between his legs and wind up over his knees, joints popping pleasurably with the pressure. Suckers broader than his palm smarted across his belly and chest, pinning his arms, and John was immobilized. He kicked and writhed, all the same.

Sherlock watched, his human arms hanging loose at his sides. John panted, pupils wide. Their eyes met, and, just for an instant, they broke the charade with a wild, shared grin. _Yes?_ Sherlock’s asked; _Yes_ , John’s replied. 

“You are strong,” Sherlock observed. John could feel anticipation trembling in his lungs. “But I am stronger.”

With no other warning, John's body was hefted upward in one violent pull, almost as forceful as a cannon blast. There was a moment of dreamlike weightlessness, and John shut his lips and teeth and barely sucked a breath through his nose before everything turned cold and stinging green.

A few white rings frothed to the surface, and a boat rocked empty on the waves.

     

☠

     

When John opened his eyes, north, south, east, and west had disappeared. Behind him was a ceiling of faint, bending light, and an endless expanse of algal blue in every other direction. 

He had stopped struggling, letting his body go limp when he was pulled under, even while it pounded with adrenaline. Now he felt fingers brushing over his chest, sliding up toward his throat. They did not grip, but settled gently against his pulse. 

Sherlock was locked around John in a living Gordian knot, controlling their slow descent. John wished he could see him more clearly, through glass, maybe, or the oblong eyes of fish. The salt burned his eyes, though not unbearably-- nothing compared to the burn that was building in his lungs. 

A last string of bubbles escaped his lips, breaking the strange, hollow silence. The limbs that bound him only flexed tighter, painful, now; feeding the malevolence in Sherlock’s blood, sating his instinct. This was the ritual in their arrangement, borne of long, patient dives-- of accidents, coughs and sputters and terrified apologies. 

John shut his eyes and wished he could put his arms around Sherlock’s neck. 

At thirty meters, John’s chest was flinching with the desire to gasp, and surf pounded in his ears. The creature who bound him was navigating John’s mortality like shoal waters. In that grey-edged moment, John felt something close to absolute peace. 

And then, a kiss.

Sherlock pressed his mouth to his lover’s in a careful seal, and John gurgled against the burn of salt water with his first, deep inhale. Pleasure overwhelmed. Sherlock gusted breathable air into John’s lungs again and again-- a gift that, from human to human, would have quickly turned to poison. 

If their mimicry of murder and the crush of teuthoidian limbs was submission to instinct, then the press of Sherlock’s lips against his was evolution. The drowning-grip finally loosened, and John pulled his arms and legs free only to wind their bodies together in gentler fashion. The siren’s curls were soft like pondmuck between his fingers. The limbs that had flirted with the power to crack bone now furled and unfurled shyly, rubbing apologies against sore skin.

They drifted, weightless, joined at every point. 

Once, Sherlock had told John about a fish which lived in the very deepest waters, the boneyards of whales and warships. She hunted by a light anchored to her head by a quavering strand, and had a body that was half squarish jaw, bristling with translucent teeth. Sherlock did not know why light was such an efficient lure in lightless place, but he knew that her mates would seek her by smell and bite through the skin of her belly. They fused to her, faster than barnacles; Sherlock knew because he had pulled them apart to see. They became one creature, with shared blood.

John felt grit against his shoulder blades, and they both startled. John lay with Sherlock above him, and his back against the sandy bottom of the ocean. He closed his eyes, swallowing carefully. Sherlock hummed into his mouth, brushing his thumbs over John’s eyelids and tapping a question against his ears. _Are you well?_

John felt as if the ocean had siphoned his strength. Perhaps it was escaping, bit by bit, with each exhale. He watched his borrowed breaths flee toward the surface in silvery capsules, like mushroom caps. He wondered if he had climaxed at some point in their encounter; it was difficult to tell, sometimes. Maybe that’s why he was so tired. 

Signalling his intention with his his fingertips, John broke his lifeline connection, remembering not to hoard his breath but exhale, in a trickle. 

Sherlock’s face was a smeared suggestion of color and shadow, like oil paint applied with the palm. John traced his cheeks and brow with his fingers, but could not speak to him. He could not tell the truth against his skin. It was intimate and isolating, all at once. 

After a few moments John began to feel Sherlock’s worry and let him join their mouths again. He sunk both hands into the soft mass of Sherlock’s lower limbs, close to where they joined his body, and noted how the delicate cups felt slicker, now, almost viscid. Sherlock puffed little, quailing sounds into his mouth, and John couldn’t tell if they were pleased or indignant. 

He buried his arms to the elbow, anyhow. He let Sherlock envelop him on the seafloor, let him pretend that they could stay like this indefinitely. 

Reality would find them soon enough. They would float up together, and John would break the surface gasping, drinking air in deep, heedless breaths. He would feel relieved and happy until he realized that Sherlock had not followed, because the rain had stopped falling. John might dive down again to find him, might kiss him again and try to murmur something against his ear, words distorted by bubbles; or he might not. He might climb into his boat and begin to row ashore, only to find a strange current pushing him, a shadow trekking in his path.

John would tend his lanterns, before anything else, climbing the lighthouse tower just ahead of the setting sun. Then he would walk across the guano-stained rocks to his own door, with one glance back toward the waves. 

Sea water would drip from his clothes over the threshold of an empty cottage. He would light the oil lamp and strip in his kitchen. Too tired to eat, he would build a fire in the stove and rub the salt from his hair and skin with a warm rag. Dried and dressed in thickspun cotton, John would climb into his narrow bed and turn his face toward the seaward window. 

Dawn would come eventually; and with dawn, perhaps, the rain.


End file.
